Notice of Syenitic Rocks from California. — Turner. 375 
because of the confluence of ice currents from the northeasl 
and northwest, was borne upward from a low and mainly 
level country to hights exceeding 500 feet above the land in 
such volume as to yield above that level the esker gravel and 
sand of this hill and also its large boulder-like enclosed mass 
of till. The arguments for high altitude and large amount of 
englacial drift based on my observations of Bird's Hill seem 
to me to be strongly re-enforced by the eskers and kames de- 
scribed in Rochester, N. Y., and the contiguous region by Prof . 
H. L. Fairclnid, and earlier in part by Mr. Charles R. Dryer 
and the present writer.* Inability to understand how the 
englacial drift was carried up through the lower quarter or 
third part of the ice-sheet, where, as in Manitoba, it was prob- 
ably a mile thick, should not forbid the acceptance of con- 
clusions which are well established by definitely observed 
features of the sublacustrine till and of associated eskers and 
kames. 
NOTICE OF SOME SYENITIC ROCKS FROM 
CALIFORNIA. t 
By U. W. Tdbnee, Washington, D. C. 
There is a present tendency among writers on petrography 
to base the classification of rocks on those characteristics 
which can be determined from the rock specimen itself. Thus 
Michel LevyJ writes: "One sees, from all that precedes, that it 
is necessary to base a rational petrographic classification upon 
contingent facts, independent of geogenetic hypotheses, and 
that the consideration of the age of rocks, from this point of 
view, is as hypothetical as that of their conditions of occur- 
rence (gisement) in the depths or at the surface. Being given 
a sample of rock from an unknown province, it is indispens- 
able and it is possible to name and describe it without amphi- 
bology. It is possible to determine from it with certainty 
neither the occurrence (gisement) nor its geological age." 
*C. R. Dryer, Am. Geologist, vol. v. pp. 202-207, with map, April 
1890. 
W. Upham, Proceedings of the Rochester Academj of Science, vol 
ii, pp. 181-200, Jan. 1893. 
H. L. Fairchild, Am. Geologist, vol. xvi, pp. 39-51, with map. July. 
189."> : Journal of Geology, vol. iv, pp. L29-159, with maps ami views, 
Feb. -March, 1896. 
tPubli.sbed by permission of the Director of the U. S. Geol. Survey. 
^Structures et classification des roches erupt ives : Paris, L889, p. 31. 
